The biggest reason people abandon calorie counting is the time it takes. Searching a database, selecting the right item, adjusting the portion size, repeating for every ingredient in a meal — it adds up to 15-20 minutes a day. Scanning changes that equation entirely. Point your phone, get the calories, and move on with your day.
Every packaged food product in the UK carries a barcode and a nutrition label. Barcode scanning connects the two instantly, giving you the calorie content (plus full nutrition data) without needing to pick up the product and read the label.
Barcode scanning is the most accurate method of calorie counting for packaged food. The data comes directly from the manufacturer's nutrition label, which must comply with UK food labelling regulations. Under these regulations, the actual calorie content of a product must be within 20% of the declared value — and most reputable manufacturers are considerably more accurate than that.
Essentially anything with a barcode: supermarket products, branded snacks, drinks, ready meals, frozen foods, cereals, dairy products, bread, sauces, condiments, and more. NutraSafe's database includes products from all major UK supermarkets, including Tesco, Sainsbury's, Asda, Morrisons, Aldi, Lidl, M&S, Waitrose, and the Co-op. For more on barcode food scanning, see our dedicated guide.
Barcode scanning does not help with a home-cooked stir fry, a meal at a restaurant, or a plate of food from a buffet. This is where AI photo scanning fills the gap.
AI photo scanning is an estimation tool, not a precision measurement. For clearly visible, simple meals, expect accuracy within 15-25% of actual calories. Mixed dishes, heavy sauces, and hidden ingredients (cooking oil, butter) reduce accuracy. That said, even an approximate estimate is considerably more useful than not tracking at all. For a deeper look at AI meal scanning, see our full guide.
The NHS recommends around 2,000 calories per day for women and 2,500 for men as a general guide. If you are tracking to manage your weight, being within 100-200 calories of your actual intake is more than precise enough. Both scanning methods comfortably achieve this level of accuracy for most meals, making them practical tools for everyday use.
One area where scanning helps enormously is navigating UK portion sizes, which are often different from what manufacturers suggest on the label.
Manufacturers set their own serving sizes, and they are often unrealistically small. Some examples:
Scanner apps help by showing calories both per serving and per 100g, making it easy to calculate the calories in the portion you actually eat. NutraSafe lets you adjust serving sizes with a simple slider, so you can match the on-screen amount to what is actually on your plate.
UK nutrition labels are required to show nutritional values per 100g (or per 100ml for liquids), which is one of the most useful features of British food labelling. This standardised figure makes it easy to compare products fairly, regardless of how the manufacturer defines a "serving". A good scanner app makes this comparison effortless.
How does scanning compare to traditional approaches?
| Method | Time per item | Accuracy | Best for |
|---|---|---|---|
| Barcode scan | 1-2 seconds | Very high (exact label data) | Packaged foods |
| AI photo scan | 3-5 seconds | Good (15-25% range) | Home-cooked, restaurant meals |
| Database search | 30-60 seconds | Moderate (depends on match) | Generic foods, produce |
| Manual calculation | 2-5 minutes | High (if weighed accurately) | Precise tracking needs |
| Estimating / guessing | 5 seconds | Low (often 30-50% off) | Not recommended |
For most people, a combination of barcode scanning (for packaged items) and AI photo scanning (for everything else) covers 90% of daily food intake in under 3 minutes total. That compares favourably to 15-20 minutes for manual logging, which is why scanning-based tracking has much higher long-term adherence rates.
Here is how scanning fits into a realistic daily routine for someone tracking their calories:
Scan the barcode on your cereal box, milk, or bread. If you are having a cooked breakfast, snap a photo of the plate. Total time: 10-15 seconds.
Packed lunch with shop-bought items? Scan the barcodes. Eating at a restaurant or canteen? Photo scan your plate. Homemade sandwich? Scan the bread and fillings individually, or photo the assembled sandwich. Total time: 15-30 seconds.
Home-cooked meals are the most common scenario. If you are cooking from packaged ingredients, scanning each barcode as you cook takes a few seconds per item. Alternatively, photo scan the plated meal. If you batch cook, scan once and save the recipe for future logging. Total time: 20-45 seconds.
Barcode scan packaged snacks. For fruit, a quick database search or photo scan works well. Do not forget to log drinks — a latte, smoothie, or glass of juice can add 100-300 calories that people often overlook.
The total daily logging time using scanning: approximately 2-3 minutes. Compare that to the 15-25 minutes that manual logging typically requires, and it becomes clear why scanning-based calorie counting is more sustainable long term.
Research published in the British Journal of Nutrition consistently shows that the most important factor in successful calorie tracking is consistency — logging every day, not just occasionally. Scanning removes enough friction that daily tracking becomes a realistic habit rather than a time-consuming chore. An imperfect scan logged every day is far more valuable than a perfect manual entry done once a week.
A few practical habits will help you get the most accurate results:
NutraSafe combines barcode scanning and AI photo scanning in one app. Scan packaged foods for exact calorie data, or snap a photo of any meal for an instant estimate. Built for UK products and portion sizes.
Download NutraSafe FreeBarcode scanning is very accurate for packaged foods — the calorie data comes directly from the manufacturer's nutrition label, which must comply with UK food labelling regulations. AI photo scanning is less precise, typically accurate to within 15-25% for simple, clearly visible meals. For practical calorie tracking, both methods are more than accurate enough. Even nutrition labels themselves are allowed a 20% tolerance under UK regulations.
Fresh produce does not have barcodes with nutrition data, so barcode scanning will not work. However, AI photo scanning can estimate calories for fresh foods by identifying them and estimating portion sizes. You can also use a food search within apps like NutraSafe to find items like "medium banana" or "100g chicken breast" and log them quickly.
Both have their place. Barcode scanning is more accurate for packaged foods because it uses exact manufacturer data. Photo scanning is more convenient for home-cooked meals, restaurant food, and fresh produce where no barcode exists. Most people who track calories regularly use both methods depending on what they are eating.
UK nutrition labels show calories per 100g and per serving, but "serving sizes" set by manufacturers are often smaller than what people actually eat. For example, a cereal serving might be listed as 30g when most people pour 50-60g. Scanner apps help by letting you adjust the portion size, and some apps like NutraSafe show both the per-serving and per-100g data so you can calculate more accurately.
A barcode scan takes 1-2 seconds from pointing your camera to seeing the full calorie and nutrition data. AI photo scanning takes 3-5 seconds. Compared to manually searching a food database (30-60 seconds per item) or weighing and calculating from raw ingredients (2-5 minutes per meal), scanning is significantly faster. Over a full day of meals and snacks, scanning saves 15-20 minutes compared to manual logging.
Last updated: February 2026